Isolation Rings for Packages and the Method of Forming the Same

ABSTRACT

A device includes a first package component, and a second package component underlying, and bonded to, the first package component. A molding material is disposed under the first package component and molded to the first and the second package components, wherein the molding material and the first package component form an interface. An isolation region includes a first edge, wherein the first edge of the isolation region contacts a first edge of the first package component and a first edge of the molding material. The isolation has a bottom lower than the interface.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.14/724,954, entitled “Isolation Rings for Packages and the Method ofForming the Same,” filed on May 29, 2015, which application is acontinuation of U.S. patent application Ser. No. 14/189,584, entitled“Isolation Rings for Packages and the Method of Forming the Same,” filedon Feb. 25, 2014, now U.S. Pat. No. 9,048,333 issued on Jun. 2, 2015,which application is a divisional of U.S. patent application Ser. No.13/485,527, entitled “Isolation Rings for Blocking the Interface betweenPackage Components and the Respective Molding Compound,” filed on May31, 2012, now U.S. Pat. No. 8,710,681 issued Apr. 29, 2014, whichapplications are incorporated herein by reference.

BACKGROUND

In the packaging of integrated circuits, device dies are bonded ontopackage components such as package substrates in a package substratestrip. The package substrates include metal connections that are used toroute electrical signals between opposite sides of the respectivepackage substrates. The dies may be bonded onto one side of a packagesubstrate strip using flip chip bonding, and a reflow is performed tomelt the solder balls that interconnect the dies and the packagesubstrates.

After the bonding of the device dies onto the package substrate strip, amolding compound is molded onto the device dies and the packagesubstrate strip. The package substrate strip is then sawed apart into aplurality of packages. Although the molding materials are generallymoisture proof, the moisture may still penetrate into the resultingpackages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIGS. 1 through 5B are top views and cross-sectional views ofintermediate stages in the formation of packages in accordance with someexemplary embodiments; and

FIGS. 6 through 8 illustrate the formation of packages in accordancewith some alternative exemplary embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare illustrative, and do not limit the scope of the disclosure.

A package and a method of forming the same are provided in accordancewith various exemplary embodiments. The intermediate stages of formingthe package are illustrated. The variations of the embodiments arediscussed. Throughout various views and illustrative embodiments, likereference numbers are used to designate like elements.

FIG. 1 illustrates a top view of a package component 20. In someembodiments, package component 20 is a package substrate strip, andhence is referred to as package substrate strip 20 hereinafter, althoughpackage component 20 may also be another type of package component suchas an interposer wafer, a device wafer, or the like. In the embodimentswherein package component 20 is a package substrate strip, packagesubstrate strip 20 includes a plurality of package substrates 22, whichare identical to each other. In some embodiments, package substrates 22are distributed uniformly in one or both of the illustrated X and Ydirections, and may have the layout of an array.

Package substrates 22 may be laminate substrates, which include aplurality of dielectric films 23 (shown in FIG. 2B) adhered togetherthrough lamination, or may be build-up substrates. Dielectric films maycomprise composite materials that are mixed with glass fiber and/orresin. Metal traces 28 and vias 30 (FIG. 2B) are formed in laminatedielectric films 23. As also shown in FIG. 2B, electrical connectors 24are formed on a surface of package substrates 22, and are connected toelectrical connectors 26 that are on the opposite side of the respectivepackage substrate 22 through metal traces 28. In some embodiments,electrical connectors 24 are metal traces, which are used for formingBump-On-Trace (BOT) connections. In alternative embodiments, electricalconnectors 24 are metal pads, metal pillars, composite connectorscomprising metal pillars and solder caps, or the like.

FIG. 2A illustrates a top view showing the bonding of package components32 onto package substrates 22 in FIG. 1. FIG. 2B illustrates across-sectional view of FIG. 2A, wherein the cross-sectional view isobtained from the plane crossing line 2B-2B in FIG. 2A. In someembodiments, package components 32 are dies (such as device diescomprising transistors), packages, or the like. Referring to FIG. 2B,the bonding may be performed through solder bonding, wherein electricalconnectors 34 of package components 32 are solder balls. In someexemplary embodiments, the bonding is a BOT bonding.

As also shown in FIG. 2B, after the bonding of package components 32onto package substrates 22, polymer 35 is dispensed to mold packagecomponents 32 and package substrates 22. In some embodiments, polymer 35is a molding compound, a molding underfill, an epoxy, or the like. Anunderfill (not shown) may be dispensed into the gaps between packagecomponents 32 and package substrates 22. Alternatively, no underfill isdispensed. Instead, polymer 35 is a molding underfill that is alsodisposed into the gaps besides molding package components 32. Polymer 35is then cured and solidified.

Referring to FIGS. 3A and 3B, a grooving is performed on packagesubstrate strip 20 to form trenches 36. The grooving may be performedusing a blade, a laser beam, or the like. Referring to FIG. 3A, trenches36 are formed between package substrates 22, and separate packagesubstrates 22 from each other. Trenches 36 may form a grid. FIG. 3Billustrates a cross-sectional view of the structure shown in FIG. 3A,wherein the cross-sectional view is obtained from the plane crossingline 3B-3B in FIG. 3A. As shown in FIG. 3B, trenches 36 penetratethrough package substrate strip 20, extend into polymer 35, and stop atan intermediate level of polymer 35. Accordingly, depth D1 of trenches36 is at least greater than thickness T1 of package substrate strip 20.Furthermore, depth D2, which is the depth of the portions of trenches 36in polymer 35, may be greater than about 20 percent thickness T2 ofpolymer 35, and may be between about 20 percent and about 80 percentthickness T2. Width W1 of trenches 36 may be between about 1,000 μm andabout 5,000 μm.

An isolation material is filled into trenches 36, and is cured(solidified) to form isolation regions 38. The resulting structure isshown in FIGS. 4A and 4B. FIG. 4B illustrates a cross-sectional view ofthe structure shown in FIG. 4A, wherein the cross-sectional view in FIG.4B is obtained from the plane crossing line 4B-4B in FIG. 4A. The topsurface of isolation regions 38 may be slightly higher than,substantially level with, or lower than, the top surfaces of packagesubstrates 22. When filled into trenches 36, isolation material 38 maybe a liquid or a gel, which has a viscosity low enough to fill into themicro-voids (not shown) in polymer 35 (FIG. 5B). Isolation regions 38may be a polymer, a resin, or the like. In some exemplary embodiments,isolation material 38 is a solder resist such as comprising Alkyd resin,acrylated epoxy resin, methacrylated epoxy resin, or the like. After thecuring, isolation regions 38 may have a density greater than the densityof the cured polymer 35 in accordance with some embodiments. Forexample, the ratio of the density of isolation regions 38 to the densityof polymer 35 may be greater than about 3 volume percent. The ratio ofthe density of isolation regions 38 to the density of polymer 35 may bebetween about 97 volume percent and about 100 volume percent inaccordance with some embodiments. The dispensing of the isolationmaterial may be performed, for example, through stencil printing.

Next, as also shown in FIG. 4B, a die saw is performed to saw thestructure in FIGS. 4A and 4B into a plurality of packages 40. Kerf lines39 are between opposite edges 38A of isolation regions 38. After the diesawing, there are remaining portions of isolation regions 38 on oppositesides of kerf lines 39. FIGS. 5A and 5B illustrate a top view and across-sectional view, respectively, of package 40. As shown in FIG. 5A,isolation regions 38 are located at the peripheral region of package 40.It is appreciated that although isolation regions 38 are referred tousing a plural form, isolation regions 38 may be parts of a samecontinuous ring, as shown in FIG. 5A. The inner edges 38A of isolationregions 38 are in contact with the edges of package component 22.

Referring to FIG. 5B, outer edges 38B of isolation regions 38 also actas the edges of package 40. Outer edges 38B are aligned to edges 35A ofpolymer 35. Inner edges 38A of isolation regions 38 are opposite toouter edges 38B, and are in contact with both package substrate 22 andpolymer 35. Furthermore, inner edges 38A are in contact with interface42 between polymer 35 and package substrate 22.

In some embodiments, isolation regions 38 form a ring encircling andcontacting interface 42. Interface 42 is likely to be the weak part inwhich moisture and detrimental chemical gases may pass through. Forexample, the moisture may travel from open air, through interface 42,and reach the internal features such as electrical connectors 24. It isrealized that the resistance to the penetration of the moistureincreases when the length of the traveling path of the moistureincreases. Accordingly, as shown in FIG. 5B, assuming if isolationregions 38 are not formed, moisture may travel from open air toelectrical connectors 24 through paths 45. When isolation regions 38 areformed, moisture may travel from open air to electrical connectors 24through paths 46, which are longer than paths 45. Since paths 46 arelonger than paths 45, the resulting package 40 has increased resistanceto the penetration of moisture and the detrimental chemical gases thanin structures that do not have isolation regions 38. As a result, sinceelectrical connectors suffer less from the moisture and detrimentalchemicals, the risk of short circuits between neighboring electricalconnectors 24 is reduced. For example, the short circuits may be theresult of the formation of dendrites between neighboring electricalconnectors 24, and the undesirable dendrites may further be formed dueto the oxidation of metal ions of electrical connectors 24, themigration of the oxidized metal ions along interface 42, and thereduction of the migrated metal ions.

FIGS. 6 and 7 illustrate the formation of package 40 in accordance withalternative embodiments. In FIG. 6, trenches 36 include wide portions36′ and narrow portions 36″, which are narrower than wide portions 36′.In the formation of trenches 36, wide portions 36′ are first formed,wherein wide portions 36′ may extend from the top surface of packagesubstrate 22 into polymer 35. Wide portions 36′ may form a grid sincewide trenches 36′ are parts of trenches 36, which forms a grid, as shownin FIG. 3A. Next, a plurality of narrow trenches 36″ is formed to extendfrom the bottom of wide portions 36′ deeper into polymer 35. Next, asshown in FIG. 7, isolation material 38 is dispensed into trenches 36 toform isolation regions 38, which also include wide portions and narrowportions. A die saw step is then performed to cut package substratestrip 20, isolation regions 38, and polymer 35 into packages 40. Therespective kerf lines 39 of the sawing are illustrated.

FIG. 8 illustrates the formation of package 40 in accordance withfurther embodiments. In these embodiments, isolation regions 38 includewide portions 38′, narrow portions 38″, and additional wide portions38′″. In the formation of the trench of isolation regions 38, thetrenches for forming portions 38′ and 38″ may be formed before thesawing of package substrate strip 20, and the trenches for formingportions 38″′ may be formed after the sawing. The filling of theisolation material 38 may be performed after the die saw.

In accordance with embodiments, a device includes a first packagecomponent, and a second package component underlying, and bonded to, thefirst package component. A molding material is disposed under the firstpackage component and molded to the first and the second packagecomponents, wherein the molding material and the first package componentform an interface. An isolation region includes a first edge, whereinthe first edge of the isolation region contacts a first edge of thefirst package component and a first edge of the molding material. Theisolation has a bottom lower than the interface.

In accordance with other embodiments, a device includes a packagesubstrate, and a device die underlying, and bonded to, the packagesubstrate. A molding compound is disposed under the package substrateand molded to the package substrate and the device die. A polymerencircles the package substrate and contacts edges of the packagesubstrate. The polymer extends from a top surface of the packagesubstrate to a level lower than a top surface of the molding compound.

In accordance with yet other embodiments, a method includes bonding afirst package component to a second package component, molding a moldingmaterial to the first and the second package components, and forming atrench penetrating through the first package component. The trenchextends into the molding material. An isolation material is filled intothe trench to form an isolation region. The isolation region and themolding material are sawed to form a package, wherein the packageincludes a portion of the isolation region.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. A package comprising: a first package component;a second package component underlying, and bonded to, the first packagecomponent; an encapsulating material encapsulating the second packagecomponent, wherein the encapsulating material and the first packagecomponent form an interface; and an isolation region comprising: a firstedge, wherein the first edge of the isolation region contacts an edge ofthe first package component and an edge of the encapsulating material;and a second edge opposite to the first edge of the isolation region,and the second edge of the isolation region is a part of an outer edgeof the package.
 2. The package of claim 1, wherein the isolation regioncomprises a top portion, and a middle portion underlying the topportion, wherein the top portion extends laterally farther toward acenter of the package than the middle portion.
 3. The package of claim2, wherein the top portion is higher than the interface, and the middleportion comprises a portion at a same level as a portion of the firstpackage component, and a portion at a same level as a portion of theencapsulating material.
 4. The package of claim 2, wherein the isolationregion further comprises a bottom portion underlying and connected tothe middle portion, and the bottom portion extends farther toward thecenter of the package than the middle portion.
 5. The package of claim1, wherein the isolation region forms a ring encircling the firstpackage component.
 6. The package of claim 1, wherein the isolationregion comprises four inner edges contacting four edges of the firstpackage component.
 7. The package of claim 1, wherein the first packagecomponent comprises a laminate substrate, and wherein the encapsulatingmaterial comprises a molding compound.
 8. The package of claim 1,wherein the isolation region has a density higher than a density of theencapsulating material.
 9. The package of claim 1, wherein the isolationregion extends lower than a bottom surface of the second packagecomponent.
 10. A package comprising: a package substrate; a device dieunderlying, and bonded to, the package substrate; an encapsulatingmaterial under the package substrate and encapsulating the device die;and a polymer-comprising material encircling, and contacting edges of,the package substrate, wherein the polymer-comprising material comprisesa top portion and a lower portion lower than the top portion, with eachof the top portion and lower portion extending from edges of the packagetoward a center of the package, and the top portion extends more towardthe center than the lower portion.
 11. The package of claim 10, whereinthe polymer-comprising material further comprises a bottom portionunderlying and connected to the lower portion, and the bottom portionfurther extends further toward the center than the lower portion. 12.The package of claim 11, wherein the top portion has a bottom surfacehigher than a top surface of the encapsulating material, and the bottomportion has a top surface lower than the top surface of theencapsulating material.
 13. The package of claim 10, wherein thepolymer-comprising material has a density greater than a density of theencapsulating material.
 14. The package of claim 10, wherein thepolymer-comprising material is configured to be dispensed in a form ofliquid, and is configured to be cured to a solid form from the liquid.15. The package of claim 10, wherein the polymer-comprising materialcomprises outer edges opposite to inner edges of the polymer-comprisingmaterial that contact the package substrate, and wherein the outer edgesof the polymer-comprising material are aligned to edges of theencapsulating material.
 16. A package comprising: a package substrate; adevice die underlying and bonded to the package substrate; anencapsulating material under the package substrate, wherein theencapsulating material is in contact with a bottom surface of thepackage substrate, and wherein the device die is encapsulated in theencapsulating material; and a polymer ring encircling the packagesubstrate and a top portion of the encapsulating material, wherein thepackage comprises an edge, with the edge of the package being verticaland straight, and the edge of the package comprises: an outer edge ofthe polymer ring; and an edge of the encapsulating material.
 17. Thepackage of claim 16, wherein the polymer ring comprises: a wide portion;and a narrow portion narrower than the wide portion, wherein the narrowportion is underlying, and connected to, the wide portion.
 18. Thepackage of claim 17, wherein each of the wide portion and the narrowportion forms a ring encircling a portion of the package substrate. 19.The package of claim 17, wherein the wide portion extends further towarda center of the package than the narrow portion.
 20. The package ofclaim 16, wherein the polymer ring has a density higher than a densityof the encapsulating material.